Conventional grinding machines used in the alimentary field are essentially constituted by a screw feeder, which is inserted in a specifically provided cylindrical seat arranged downstream of an inlet, is turned by a specifically provided motor and conveys the food towards a plurality of blades which rotate coaxially thereto, are fitted on the same driving shaft as the screw feeder, are grouped in a pack and are alternated with perforated screening diaphragms.
The diaphragms are arranged in a gradually decreasing sequence as regards both the density of the holes that affect each diaphragm and the diameter of the holes, so as to gradually provide, as the food advances outwards, a progressively finer reduction of the particle size of the mass.
However, especially in the processing of very dense food or of food having a fleshy pulp, the resistance that occurs when the mass passes between the diaphragms generates a very intense pressure, which is transmitted and distributed to said diaphragms, to the rotating blades and to the screw feeder.
Accordingly, this entails, especially in the industrial use of grinding machines, the use of motors with a high power rating, even as high as 70 HP, in order to overcome the resistance opposed by the mass being processed.
As a further consequence, there is provided a gradual deterioration not only of the sharpness of the blades but also of their structure, which by wearing very quickly require their replacement on the average every 4-5 working hours in addition to releasing microscopic fragments into the food.
Another problem of the known art in this field is the fact that in the diaphragms, the perforations that allow passage through them are distributed on each diaphragm with a decreasing density with respect to their surfaces, and this worsens the problem of the pressure applied by the food mass.